For office work, chairs and seats with height adjustment are frequently used; in addition, user comfort is enhanced if the seat can tilt gently, thus affording easy selection of the most comfortable position. Numerous types of chairs have been designed to achieve this effect; however, there is a need for a chair in which this tilt can be adjusted, with variation in hardness (degree of resiliency), and completely locked if so required, with adjustments effected by simple actions or controls.